Various techniques are known for dyeing a textile substrate in a pattern configuration. For example, it is well known that textile substrates may be dyed in a pattern configuration using a heat transfer printing process. In such processes, heat-sublimable dyes may be arranged in a pattern on an inert sheet such as paper. The paper is then brought into close association with the substrate surface to be dyed under conditions of heat and pressure. The dye sublimes and is transferred to the substrate in the vapor phase, where it condenses and is absorbed into the fibers comprising the substrate.
Using another technique, U.S. Pat. No. 3,619,103, to Williams, et al. describes a process for producing heat-induced effects on textiles or the like by means of one or more heated rollers. According to the teachings of Williams, et al., migration, heat fixation, and development of dyes on a textile substrate may be greatly accellerated through the use of such roller. The process of Williams et al., however, relates to a process wherein dye migration from one portion of the substrate to another is employed as the primary means to achieve a desired pattern. As a result of the liquid phase migration phenomenon, patterning the face of a fabric necessarily involves the patterning of the back of the fabric as well, and patterned areas tend to exhibit slightly "fuzzy" or indistinct edges. Also, large expanses of dyed fabric exhibit an "edge effect", wherein the edge of the dyed area contains more dye than the interior of such area, making such areas exhibit light and dark variations of the color rather than a single, uniform color. Furthermore, Williams, et al. does not suggest that an unpatterned textile substrate may be applied with dye in a pattern configuration and, substantially simultaneously, the dye in the dyed areas fixed, without the need for an additional process step. The process of Williams, et al. is also somewhat limiting in the sense that the substrate must generally be wet or have a high moisture content to permit patterning, and the time required by Williams, et al. for the preferred source of heat, i.e., the roller, to transfer sufficient heat to the substrate to initiate appreciable migration is relatively slow when compared to the process of the invention disclosed herein.
Processes which utilize the localized application of heat to impart a visual surface effect on a textile substrate are also common. Embossing techniques in which a heated roll or other heated member is pressed against the surface of a textile substrate in order to impart various visual surface effects such as surface sculpturing are well known in the art. As an example of patterning by means of heated air, U.S. Pat. No. 4,364,156 to Greenway, et al. discloses an apparatus for heat-treating the surface of a textile substrate by the pattern-wise application of a heated fluid such as air from selected locations along a slot in an elongate manifold, the fluid containing sufficient thermal energy to shrink or otherwise permanently thermally modify the visual appearance of the substrate in those areas contacted by the fluid. It is believed this technique results in a much more uniform heat treatment of the substrate as a result of, among other things, superior heat transfer to the individual yarns comprising the substrate surface. Under many circumstances, however, a higher degree of visual contrast in the thermally modified areas is desired than is commonly obtained using this technique.
It is desirable under some circumstances to modify the color or hue of the areas contacted by the heated fluid streams, relative to the color or hue of the background. Differential dyeing techniques, wherein a substrate comprising synthetic fibers is initially heat treated to modify the quantity of dye later adsorbed by the treated fibers in a post-treatment dyeing step, are known in the art. Such differential dyeing techniques present a substantial difficulty in observing or inspecting the pattern areas for quality control purposes before the fabric is dyed. Prior to dyeing, some textile fabrics, when pattern-wise heat treated sufficiently to change significantly the degree of dye take-up in those heat treated areas, exhibit little visual contrast between the treated and untreated areas, making it extremely difficult to observe, and therefore inspect, the patterned areas prior to the dyeing step. The process of this invention eliminates this problem by applying the dye to the fabric prior to the patterning step rather than following such step. The dye which has been subjected to heat appears visually different than, and often darker than, dye which has had no such heat exposure, thereby making the heat treated areas readily visible during the patterning step.
Described herein is a novel process for patterning textile substrates wherein selected areas having enhanced contrast or a multi-tone pattern effect may be generated by the local, pattern-wise application of heat to areas of the substrate wherein a dyed has been applied. This process may also be employed where simultaneous dyeing and sculpturing, in perfect registry, is desired. This process overcomes the disadvantages recited above in connection with alternative dyeing processes.